Minimal Preparation Techniques for Porcelain Laminate Veneers

In this article we will take the visual diagnostic try-in to complete a minimal preparation veneer case. This will be exemplified by the case study along with a step-by-step series of photographs.

At the time of presentation the patient, who we use to demonstrate this technique, was a 25 year old male who ran his own highly successful company and dealt with customers on a day-to-day basis. He wanted to close the gaps between his teeth, he also felt that the central incisors were not dominant enough and were a little too rounded. He felt this made him look immature which was inconstant with his status. He wanted a perfect, lighter smile.

Treatment Plan

As shown in the first article this is based on a wax-up. The putty matrix is filled with the provisional material and this is seated over the teeth. This material can be Luxatemp (available from Minerva). For trial smile purposes the shade closest to the final desired shade should be used.

He was delighted with what he saw and upon being reassured that the preparations would be very minimal and all in enamel he decided to proceed with 10 porcelain laminate veneers to close the spaces, widen the buccal corridor, and make the centrals more dominant by increasing their length by approximately 1mm. This visual try-in also gave us the opportunity to assess the phonetics and functionality of the restorations.

Prior to this restorative treatment plan he underwent a full hygiene programme to improve his gingival health and home care regime, and Zoom in surgery whitening of his lower teeth only, together with home trays. We tend to avoid whitening the teeth to be prepared so that the natural underlying colour can be accurately gauged. This will allow a more accurate final colour for the porcelain, especially if the plan is to make the teeth brighter. If these teeth are whitened to a much brighter colour, the underlying tooth colour will return back to its original shade over time so that the veneers themselves may then look darker.

Preparation

Even if the preparations are going to be very minimal, for piece of mind of the patient it is still a good practice to use Local anaesthetic.

For this case we will be using felpspathic porcelain rather than pressed porcelain. Thus we only need up to 0.5 mm thickness of porcelain rather than 0.7mm as with pressed ceramics. Depth cuts are made through the visual try-in with a 0.5mm depth cutting bur (number 828 314 026, available from Komet through West One Dental - this is part of the Co-Op. R8 preparation bur kit, www.coopr8.com). For the preparation through the Luxatemp, ensure you use a dark shade if the teeth are light or a light shade if the teeth are dark so that the underlying tooth can be seen once the depth cuts are made. Place these depth cutes in the mid-facial and incisal areas and not at the cervical areas as the enamel is only 0.3mm thick in this region. The aim is to keep the preparation all within enamel. It is easy to visually inspect the cervical preparation depth by assessing chamfer margin depth.

A sharp pencil is used to highlight these depth cuts to aid visualisation of what has been prepared. Appropriate incisal reduction for the incisal prescription is then completed. This can range from a minimum of 1.5 mm, up to 2.5 mm if very heavy incisal translucency is required. This reduction is completed on the trial smile again to ensure space is only created where it is needed. To avoid the material becoming dislodged during the preparation, it is possible to spot tack the provisional into place using a little acid etch on the mid facial aspect of the tooth, as this area will be cleaned of any resin when the preparations are finalised.

When closing spaces the veneer needs to emerge from a sub-gingival position to compress the gingivae slightly in order to avoid a black triangle. This emergence profile can be aided by troughing the gingival sulcus with a laser.

The Luxatemp can now be carefully removed, being especially careful to avoid trauma to the gingival tissue if the material has become locked interdentally. Once the material is removed it is possible to see the black lines where the depth preparation has extended through to the natural tooth tissue. These highlighted areas indicate were tooth reduction is required for the porcelain veneer. They need to be removed level with the base of the depth cut. HOWEVER if they are not present as is the case on the majority of teeth demonstrated here, no further facial reduction is required! The preparations are now finalised with the appropriate finishing line (ideally supra-gingivally unless there is severe discolouration) and ensuring that everything is confluent with no sharp edges or angles. If these are present stresses can be created within the veneers resulting in possible fracture either at cementation or at a later date.

Once the preparations are thought to be finalised the putty index can be reloaded with Luxatemp and allowed to set. It can then be removed to check that there is no shine through of the underlying tooth structure indicating that insufficient tooth has been removed in this area. It is better to find this out now rather than when the impressions have been taken and the provisional made, as this will necessitate these procedures to be repeated following further preparation. This is belt and braces but takes little time and ensures accuracy.

Conclusion

Acknowledgements and References